1. Field of the Invention
The present invention relates to a home agent for receiving a communication packet that is sent out to a home address of a mobile terminal as a destination and then transferring this communication packet to a mobile terminal connected to a foreign network and a mobile communication system using this home agent and, more particularly, a home agent and a mobile communication system capable of achieving improvement in a performance of an overall mobile communication system.
2. Description of the Related Art
FIG. 3 is a view showing a configuration of the mobile communication system in the related art (See JP-B-3496641 and JP-B-3601464, for example.). In FIG. 3, mobile terminals (each also called a mobile node (MN)) 10(1) to 10(3) can be carried with the user, and a subnetwork to be connected is changed following upon the movement of the mobile terminals 10(1) to 10(3). Also, the mobile terminals 10(1) to 10(3) conform to a communication protocol MIPv6 (Mobile Internet Protocol version 6), and have a mobile node function in the so-called mobile IP respectively. Then, the mobile terminals 10(1) to 10(3) have a route optimizing section Rt1 that optimizes a communication route respectively.
Also, communication destination terminals (each also called a correspondent node (CN)) 20(1) to 20(3) have a route optimizing section Rt2 respectively, and perform communication with the mobile terminals 10(1) to 10(3). The route optimizing section Rt2 optimizes the communication route in answer to the request from the route optimizing section Rt1 of the mobile terminals 10(1) to 10(3).
A home network HN is a subnetwork to which the mobile terminals 10(1) to 10(3) are connected originally. Also, foreign networks FN1 to FN3 are subnetworks to which the mobile terminals 10(1) to 10(3) moved from the home network HN are connected actually.
In FIG. 3, by way of example, the mobile terminal 10(1) is connected to the foreign network FN1, the mobile terminal 10(2) is connected to the foreign network FN2, and the mobile terminal 10(3) is connected to the foreign network FN3. In this case, various nodes such as other terminals, routers, servers, etc. other than the mobile terminals 10(1) to 10(3) are present in the home network HN and the foreign networks FN1 to FN3, but their illustration is omitted herein.
A home agent (HA) 30 includes a transiting section 31 and internal resources 32, and operates on the node in the home network HN. Also, the home agent 30 conforms to the MIPv6, and controls and relays the communication among a plurality of terminals 10(1) to 10(3) and 20(1) to 20(3) by using functions provided by the MIPv6.
The transiting section 31 receives the communication packet being sent out to the mobile terminals 10(1) to 10(3) from the communication destination terminals 20(1) to 20(3) when the mobile terminals 10(1) to 10(3) stay in the foreign networks FN1 to FN3, and transfers the communication packet to the mobile terminals 10(1) to 10(3). Conversely the transiting section 31 receives the communication packet being sent out to the communication destination terminals 20(1) to 20(3) from the mobile terminals 10(1) to 10(3), and transfers the communication packet to the communication destination terminals 20(1) to 20(3). The internal resources 32 are registers, memories, and the like used for data processing, computing, data storing, etc. in the transiting section 31 and the home agent 30.
A backbone network 100 consists of the IP network, the Internet, or the like, for example. The home network HN, the foreign networks FN1 to FN3, and the communication destination terminals 20(1) to 20(3) are connected to the backbone network 100.
In this case, the home address and the care of address are allocated to the mobile terminals 10(1) to 10(3). The home address gives the address that is allocated uniquely to the mobile terminals 10(1) to 10(3) independent of the subnetwork, and gives the same network address as that in the home network HN. The care of address gives the address that is allocated to the foreign networks FN1 to FN3.
Then, the home agent 30 stores the home address and the care of address of the mobile terminals 10(1) to 10(3) in its memory (not shown) to correlate with each other. Accordingly, the transiting section 31 transfers the received packet based on the correlation of the address stored in the memory.
Also, the communication destination terminals 20(1) to 20(3) store in advance only the home addresses of the mobile terminals 10(1) to 10(3) in their memories (not shown).
An operation of such system will be explained with reference to FIG. 4 and FIG. 5 hereunder.
An operational example in which the communication destination terminal 20(1) performs communication with the mobile terminal 10(1), the communication destination terminal 20(2) performs communication with the mobile terminal 10(2), and the communication destination terminal 20(3) performs communication with the mobile terminal 10(3) will be explained herein.
In getting into communication with the mobile terminal 10(1), at first the communication destination terminal 20(1) sends out the communication packet to the home address of the mobile terminal 10(1) as the destination. That is, the communication destination terminal 20(1) sends out the packet to the home agent 30. Then, the transiting section 31 of the home agent 30 receives the packet, and then transfers the packet to the mobile terminal 10(1) (L1 in FIG. 4). In this case, because the transiting section 31 executes the transiting process, the internal resources 32 of the home agent 30 are used.
Then, in getting into communication with the mobile terminal 10(2), at first the communication destination terminal 20(2) sends out the communication packet to the home agent 30. Then, the transiting section 31 of the home agent 30 transfers the communication packet to the mobile terminal 10(2) (L2 in FIG. 4). In this case, because the transiting section 31 executes the transiting process, the internal resources 32 of the home agent 30 are further used. Thus, there are not sufficient resources to carry out newly the transiting process.
In addition, in getting into communication with the mobile terminal 10(3), at first the communication destination terminal 20(3) sends out the communication packet to the home agent 30. In this case, because the internal resources 32 of the home agent 30 are insufficient, the transiting section 31 cannot execute the transiting process and thus the home agent 30 cannot receive the communication packet (L3 in FIG. 4).
In contrast, when the communication is held between the communication destination terminal 20(1) and the communication destination terminal 20(2), the route optimizing section Rt1 of the mobile terminals 10(1), 10(2) request the route optimizing section Rt2 of the communication destination terminals 20(1), 20(2) to use the communication route bypassing the home agent.
Then, the mobile terminals 10(1), 10(2) send out the care of address to the communication destination terminals 20(1), 20(2). Then, the route optimizing section Rt1, Rt2 cooperate with each other to get mutual authorizations, or the like, and then select the communication route bypassing the home agent 30. Thus, the terminals 10(1), 10(2), 20(1), 20(2) perform the communication directly via the selected route (L4, L5 in FIG. 5). Accordingly, there is no need for the transiting section 31 to execute the transiting process of the communication packet, and thus the internal resources 32 become free.
Further, in getting into communication with the mobile terminal 10(3), at first the communication destination terminal 20(3) sends out the communication packet to the home agent 30. At this time, because the home agent 30 has the internal resources 32 enough and to spare, the transiting section 31 of the home agent 30 transfers the communication packet to the mobile terminal 10(3) (L6 in FIG. 5)
JP-B-3496641 and JP-B-3601464 are referred to as related art.
In this manner, once the communication is held between the terminals 10(1) to 10(3), 20(1) to 20(3) via the transiting section 31 of the home agent 30, the route optimizing section Rt1, Rt2 of the terminals 10(1) to 10(3), 20(1) to 20(3) switch the route not to pass through the home agent 30. Therefore, the internal resources 32 of the home agent 30 are recovered.
However, the route optimizing section Rt1 of the terminals 10(1) to 10(3) decide independently whether or not such route optimizing section Rt1 request the route optimizing section Rt2 of the communication destination terminals 20(1) to 20(3) to optimize the route, based on the states of own terminals 10(1) to 10(3), a situation of the backbone network 100, and the like, and are not affected by a situation of the internal resources 32 of the home agent 30. Therefore, such a situation is caused that the transiting section 31 cannot execute newly the transiting process because of a lack of the internal resources 32 of the home agent 30. As a result, such a problem existed that the performance of the overall mobile communication system and thus a communication efficiency is lowered.